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Analog Devices Inc. LT3475EFE#PBF
- Part No.:
- LT3475EFE#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- LED Drivers
- Package:
- 20-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Datasheet:
-
LT3475EFE#PBF.pdf
- Description:
- IC LED DRV RGLTR PWM 20TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,234
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Product details
Overview
LT3475EFE#PBF from Analog Devices (formerly Linear Technology) is a dual-channel, constant-current step-down DC/DC LED driver IC with integrated 1.5A bipolar NPN power switches, high-side current sensing, and true-color PWM dimming up to 3000:1. It operates from 4V to 36V input, delivers precise 50mA–1.5A per channel, and supports grounded-cathode LED configurations for automotive lighting and display backlighting.
For engineers reviewing the LT3475EFE#PBF datasheet, LT3475EFE#PBF pinout, LT3475EFE#PBF application, or LT3475EFE#PBF equivalent, key selection criteria include its 20-lead TSSOP thermal package, 600kHz switching frequency (RT = 24.3kΩ), open-LED protection (LT3475 variant), and dual-channel anti-phase operation for reduced input ripple.
Technical Context
The LT3475EFE#PBF implements a current-mode PWM architecture with two independent master/slave oscillators enabling anti-phase switching-reducing input capacitor RMS current and output voltage ripple. Each channel features an internal 0.067Ω current-sense resistor, VC error amplifier feedback, and programmable switching frequency (200kHz–2MHz) via RT pin.
It integrates open-circuit LED protection clamping OUT/LED pins to 14V (LT3475), thermal shutdown, frequency foldback under overload, and undervoltage lockout at 3.7V. The high-side sense topology enables direct cathode grounding, eliminating floating return paths required by low-side drivers.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 36V operating; 40V absolute max - supports 12V/24V automotive rails and wide industrial supplies. |
| Output Current per Channel | 50mA to 1.5A adjustable via VADJ - enables single white LED (3.4V) or two-series strings (6.8V) with ±3% accuracy over temp. |
| Switching Frequency | 600kHz typical (RT = 24.3kΩ); 200kHz–2MHz programmable - balances inductor size vs. efficiency in space-constrained designs. |
| Dimming Ratio | 3000:1 true-color PWM - maintains chromaticity across full brightness range without color shift. |
| Package | 20-lead TSSOP with exposed thermal pad - θJA = 30°C/W; requires PCB ground plane & thermal vias for 125°C junction operation. |
| Protection Features | Open-LED clamp (14V), thermal shutdown, frequency foldback, UVLO (3.7V), and cycle-by-cycle current limiting - ensures robustness in fault conditions. |
| Operating Temperature | –40°C to +85°C (E-grade) - qualified for automotive cabin and industrial ambient environments. |
Pinout & Package
LT3475EFE#PBF uses a 20-lead plastic TSSOP package with exposed thermal pad (Pin 21) electrically and thermally connected to GND. The package requires soldering the exposed pad to a large PCB ground plane with ≥4 thermal vias for thermal performance compliance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| OUT1, OUT2 (Pins 1, 10) | Current-sense resistor input | Connects to inductor and output capacitor; forms high-side current sense node with LED pin. |
| LED1, LED2 (Pins 2, 9) | Current-sense resistor output / LED anode connection | Direct anode tie point; enables grounded-cathode LED configuration and open-LED detection. |
| VIN (Pins 5, 6) | Main power input | Dual VIN pins reduce trace inductance; must be locally bypassed with ≥4.7μF X7R ceramic capacitor. |
| SW1, SW2 (Pins 4, 7) | Internal switch collector output | Drives external inductor/diode; voltage swings from GND to VIN + boost voltage. |
| BOOST1, BOOST2 (Pins 3, 8) | Charge-pump drive voltage supply | Provides >VIN voltage to saturate internal NPN switches; requires external Schottky diode + capacitor. |
| GND (Pins 15, 21) | Power and signal reference | Pin 21 is exposed thermal pad - mandatory GND connection for electrical integrity and thermal dissipation. |
| RT (Pin 14) | Oscillator timing control | Resistor-to-GND sets switching frequency; 24.3kΩ yields 600kHz; tolerance directly impacts frequency accuracy. |
| SHDN (Pin 16) | Enable/disable control | 2.6V threshold enables regulator; <0.3V shuts down bias circuits - usable as accurate UVLO with external divider. |
| PWM1, PWM2 (Pins 20, 11) | Digital dimming interface | Active-low control disconnects VC amplifier; preserves state during off-time for linear 3000:1 dimming. |
| VADJ1, VADJ2 (Pins 19, 12) | LED current programming input | Voltage-controlled current setpoint: ILED = 1.5A × VADJ/1.25V; ties to REF for full 1.5A. |
Key Features
| Feature | Design Value |
|---|---|
| True-color PWM dimming | 3000:1 ratio with no perceptible color shift - achieved by preserving constant LED current amplitude during PWM on/off cycles. |
| Anti-phase switching | 180° phase offset between channels reduces input ripple current by ~70%, allowing smaller input capacitors. |
| Integrated high-side current sense | 0.067Ω internal resistor eliminates external sense components and enables grounded-cathode LED layout. |
| Open-LED protection | Clamps LED/OUT pins to 14V and forces low-frequency operation - prevents overvoltage damage when LEDs fail open. |
| Programmable switching frequency | 200kHz–2MHz via single RT resistor - enables optimization of inductor size, efficiency, and EMI profile per application. |
Applications
| Automotive Exterior Lighting | Architectural Accent Lighting |
|---|---|
Use Scenario: Driving dual high-brightness white LED strings in headlamp or DRL modules with strict thermal and EMC constraints. IC Role / Device Role / Timing Role: Dual-channel constant-current source with anti-phase switching and open-LED fault reporting. Use Value: Enables compact, thermally efficient 12V/24V headlamp design with built-in fault protection and 3000:1 dimming for adaptive driving beams. |
Use Scenario: Powering distributed RGBW LED strips in commercial façade or museum lighting where color fidelity and smooth dimming are critical. IC Role / Device Role / Timing Role: Independent current-regulated channel controller supporting synchronized or staggered PWM dimming. Use Value: Maintains consistent white point across full dimming range while reducing input capacitor count via anti-phase operation. |
| Industrial Display Backlighting | Medical Instrument Indicators |
Use Scenario: Backlighting high-resolution TFT panels in ruggedized HMIs requiring stable luminance over temperature and long service life. IC Role / Device Role / Timing Role: Precision current source with ±3% LED current accuracy and thermal derating support. Use Value: Eliminates luminance drift across –40°C to +85°C operating range; high-side sensing simplifies PCB layout versus low-side alternatives. |
Use Scenario: Driving status LEDs in diagnostic equipment where reliability, low standby current, and fault visibility are mandated. IC Role / Device Role / Timing Role: Fault-tolerant LED driver with <2μA shutdown current and open-circuit detection. Use Value: Ensures indicator visibility during power-up/fault conditions while minimizing system standby power draw. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-channel constant-current LED driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3783EFE#PBF | Single-channel, higher-voltage (60V) boost/buck-boost LED driver; no integrated current sense; requires external MOSFETs. | Suitable for high-Vf LED strings (>30V) but lacks dual-channel integration and true-color PWM. | Select when driving >25V LED strings or needing >36V input; not drop-in for LT3475EFE#PBF's dual 1.5A step-down role. |
| MAX16820ATP+ | Dual-channel, 1.2A peak current; 4.5V–40V input; uses external sense resistors; no open-LED protection. | Lower max current and no integrated open-circuit clamp; requires additional fault monitoring circuitry. | Consider for cost-sensitive designs where 1.2A/channel suffices and external sensing is acceptable; verify thermal design for same PCB footprint. |
Compared with LTC3783EFE#PBF and MAX16820ATP+, the LT3475EFE#PBF uniquely integrates dual 1.5A step-down regulation, high-side current sensing, open-LED protection, and 3000:1 true-color PWM in a single 20-lead TSSOP - reducing BOM count and layout complexity for mid-power automotive and industrial LED systems.
Availability
LT3475EFE#PBF is available at Aetrix Electronics and suitable for automotive exterior lighting, architectural accent lighting, and industrial display backlighting requiring stable component supply, long-term lifecycle support, and AEC-Q200-aligned reliability.
Supply support for LT3475EFE#PBF includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Analog Devices acquired Linear Technology in 2017 and maintains its legacy precision analog and power management product lines with full datasheet, simulation model, and application support.
The LT3475 series belongs to Linear's high-reliability LED driver portfolio, designed specifically for automotive, industrial, and architectural lighting systems demanding accurate current regulation, fault resilience, and compact thermal packaging.
FAQ
What is the maximum LED string voltage supported by LT3475EFE#PBF?
The LT3475EFE#PBF supports up to 14V on its LED/OUT pins due to internal open-LED clamping - confirmed in Absolute Maximum Ratings and Electrical Characteristics tables. This limits usable LED string voltage to ≤14V per channel. For higher-voltage strings, the LT3475-1 variant (25V rating) or external protection circuitry is required.
Does LT3475EFE#PBF require external current-sense resistors?
No. The LT3475EFE#PBF integrates a precision 0.067Ω high-side current-sense resistor per channel, eliminating external sense components and associated layout errors. This is explicitly stated in the Features section and verified in the Block Diagram and Pin Functions.
How does anti-phase switching reduce input ripple in LT3475EFE#PBF?
The LT3475EFE#PBF configures its dual channels with 180° phase offset (150°–210° typical), causing input current pulses to partially cancel. As shown in Typical Performance Characteristics, this reduces RMS input ripple current by ~70%, enabling smaller input capacitors and lower EMI without sacrificing channel independence.
What is the purpose of the exposed thermal pad (Pin 21) on LT3475EFE#PBF?
Pin 21 is an exposed copper pad electrically connected to GND and thermally coupled to the die. Per the Package Description and Pin Configuration, it must be soldered to a large PCB ground plane with ≥4 thermal vias to achieve θJA = 30°C/W and prevent junction temperature exceedance at full load.
Can LT3475EFE#PBF drive two independent LED strings with different currents?
Yes. Each channel has independent VADJ1/VADJ2 inputs, allowing separate current programming: ILED = 1.5A × VADJ/1.25V. The datasheet confirms individual adjustment capability in Pin Functions and Electrical Characteristics (e.g., VADJ bias current spec per pin).
LT3475EFE#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 20-TSSOP (0.173", 4.40mm Width) Exposed Pad
- Packaging:
- Tube
- Product Status:
- Active
- Type:
- DC DC Regulator
- Topology:
- Step-Down (Buck)
- Internal Switch(s):
- Yes
- Number of Outputs:
- 2
- Voltage - Supply (Min):
- 3.7V
- Voltage - Supply (Max):
- 36V
- Voltage - Output:
- -
- Current - Output / Channel:
- 1.5A
- Frequency:
- 200kHz ~ 2MHz
- Dimming:
- PWM
- Applications:
- Backlight, Lighting
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- Automotive
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-TSSOP-EP
LT3475EFE#PBF FAQ
1.How can I place an order for LT3475EFE#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3475EFE#PBF on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for LT3475EFE#PBF reliable?
The price and inventory of LT3475EFE#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3475EFE#PBF is usually 5 days.
3.What payment methods are accepted for LT3475EFE#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3475EFE#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3475EFE#PBF?
LT3475EFE#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3475EFE#PBF order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for LT3475EFE#PBF?
For technical support, including LT3475EFE#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3475EFE#PBF requirements.
6.How does Aetrix verify that LT3475EFE#PBF is sourced from the original manufacturer or authorized distributors?
All LT3475EFE#PBF products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that LT3475EFE#PBF meets industry standards.
7.What is the process for return or replacement of LT3475EFE#PBF?
All LT3475EFE#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3475EFE#PBF, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The LT3475EFE#PBF part is unused and in its original packaging.
Return procedure for LT3475EFE#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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